Step changes listener in construction heuristic phase

Question

In OptaPlanner, I noticed that there is variable changes listener for every move. And SolverEventListener for bestSolutionChanged which is calculated after every phases. However, I could not find to catch the changes in each step end.

Any suggestions to listen the Step changes in Construction Heuristic phase?

Answer 1

To listen to to events on a level of steps and phases, you 'll need to use an internal listener called PhaseLifecycleListener. For example the internal benchmarker code uses it:

StepScoreSingleStatisticListener listener = new StepScoreSingleStatisticListener();
((DefaultSolver) solver).addPhaseLifecycleListener(listener);
// solver.solve(...);
((DefaultSolver) solver).removePhaseLifecycleListener(listener);

The implementation could look something like this:

private class StepScoreSingleStatisticListener extends PhaseLifecycleListenerAdapter {

    @Override
    public void stepEnded(AbstractStepScope stepScope) {
        ...
    }

}

Warning: This is internal API, not backwards compatible in future releases, not documented, not for the faint hearted, use at own risk, you're not in Kansas anymore Dorothy, ... :)